To examine the effect of pulmonary rehabilitation on the quality of sleep and nocturnal oxygenation in patients with chronic obstructive pulmonary disease. To investigate the relationship between changes in sleep quality and changes in each of the following: aerobic exercise capacity, respiratory muscle performance and nocturnal growth hormone secretion. This will be accomplished by comparing measures of sleep quality, nocturnal oxygenation, exercise capacity, respiratory muscle performance and growth hormone secretion before and after rehabilitation.